Conventionally, in the field of manufacturing semiconductor devices, LCDs and the like, there has been employed a plasma processing apparatus which performs plasma etching or plasma CVD by means of generating a plasma. In such plasma processing apparatus, the plasma is generated in a depressurized atmosphere of a processing chamber. Accordingly, as a means to maintain a target substrate in a vacuum chamber, an electrostatic chuck is widely utilized.
As for the plasma processing apparatus using the electrostatic chuck, it may be difficult to separate the target substrate from the electrostatic chuck after stopping an application of a DC voltage to the electrostatic chuck, because the target substrate is kept strongly attached to the electrostatic chuck due to residual charges remaining in the electrostatic chuck. Thus, the target substrate would be forcibly detached from the electrostatic chuck, which may incur damage thereon. To solve this problem, there is known a method of reducing the speed of lifting the target substrate if an attraction force by residual charges is over a specific level (see, for example, Japanese Patent Laid-open Publication No. 2001-257252). Further, there is also known a method of lifting the target substrate by a pressure of a thermally conductive gas supplied to a rear surface of the target substrate if an attraction force by residual charges is over a certain level (see, for example, Japanese Patent Laid-open Publication No. 2000-200825).
The purpose of the aforementioned conventional methods is to separate the target substrate from the electrostatic chuck without inflicting a damage on the target substrate in the event that the amount of residual charges is so great that the target substrate cannot be readily separated from the electrostatic chuck. However, once such occasion arises, it takes time to separate the target substrate from the electrostatic chuck and unload it outside the processing chamber, resulting in a reduction of productivity. Further, since these methods do not reduce the residual charges in the electrostatic chuck in the process of separating the target substrate physically, they do not provide a fundamental solution to the problem.